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Experimental discovery of a topological Weyl semimetal state in TaP

DOI: 10.1126/sciadv.1501092 DOI Help

Authors: S. Y. Xu (Princeton University) , I. Belopolski (Princeton University) , D. Sanchez (Princeton University) , C. Zhang (Peking University) , G. Chang (National University of Singapore) , C. Guo (Peking University) , G. Bian (Princeton University) , Z. Yuan (Peking University) , H. Lu (Peking University) , T. R Chang (National Tsing Hua University) , P. P Shibayev (Princeton University) , Mykhaylo Prokopovych (Swiss Light Source) , N. Alidoust (Princeton University) , H. Zheng (Princeton University) , C. C Lee (National University of Singapore) , S. M. Huang (National University of Singapore) , R. Sankar (National Taiwan University) , F. Chou (National Taiwan University) , C. H. Hsu (National University of Singapore) , H. T Jeng (National Tsing Hua University) , A. Bansil (Northeastern University) , T. Neupert (Princeton University) , V. N. Strocov (Swiss Light Source) , H. Lin (National University of Singapore) , S. Jia (Peking University) , M. Z. Hasan (Princeton University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Advances , VOL 1 , PAGES e1501092 - e1501092

State: Published (Approved)
Published: November 2015

Abstract: Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal’s surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission.

Journal Keywords: Weyl Fermion; Fermi arc; Topological physics; Weyl semimetal; Topological insulator

Subject Areas: Physics

Instruments: I05-ARPES

Other Facilities: Stanford Synchrotron Radiation Lightsource Advanced Light Source